Reduce your energy usage by 1/2with Net Zero energy design concepts

WHITEPAPER

NET ZERO IS POSSIBLE, BUT GETTING HALFWAY THERE IS MORE REALISTIC.BY JOHN SAUER, PE, LEED AP

architecture engineering planning interiors800.565.4855www.bsalifestructures.com

REDUCE YOUR ENERGY USAGE BY 1/2

The 2030 Challenge - sustainable buildings are becoming the norm.

The 2030 Challenge, which has been adopted by AIA, ASHRAE, USGBC and supported by the United State Department of Energy, requires all new commercial buildings to have a 100% fossil fuel reduction by the year 2030. If we do not move down the path of less energy intensive buildings voluntarily, the federal government will either legislate it or the department of energy will decree it. That is one reason why the organizations listed above have adopted the 2030 challenge.

This may sound aggressive, and in fact, it is. The 2030 challenge also has some intermediate goals (Figure 1). As you can see, we have already passed the 2010 goal of a 60% reduction in fossil fuel use and I would suggest that not very many new buildings meet this goal. Why is that? I believe that most owners of new buildings do not understand the dynamics of how to achieve a high performance building let alone how to achieve a net zero energy building. To the owner, that sounds expensive and will not meet the business case for the building. Therefore, we continue down the same path of the tried and true design/cost model approach.

It’s time to look at this in another way. In most cases, high performance buildings can be designed and built for just a few percent more than traditional buildings and in many cases for the same cost. High performance buildings have beneficial trade-offs. Example - we can trade a better performing building envelope for a smaller heating and cooling system. We can trade the cost of low flow plumbing fixtures for a smaller water heater, etc. The best part of this approach - a reduction in operating costs for the life of the building while meeting the 2030 Challenge. Lower operating cost can mean lower space rental costs and increased marketability.

This whitepaper illustrates how to design a Net Zero Energy Building. And if you train to go all the way, getting half way there is easy. In actuality, it’s the first half that costs the least and pays off the most.

FIGURE 1 | The 2030 Challenge

REDUCE YOUR ENERGY USAGE BY 1/2

There are several definitions of a net zero energy building. The most frequently accepted definition is: A net zero energy building is defined as one which produces by on-site renewable energy sources as much energy as it uses. It is like being energy self sufficient. This definition applies to what is called “site energy”. It does not take into account the energy used to transport the energy to the building site (source energy).

The building is still connected to the electrical grid because sometimes the building will use more energy than it makes while at other times the building will make more energy than it uses. This is what the 2030 challenge is all about, net zero energy.

What is a net zero energy building?

Net zero energy refers to site energy only

REDUCE YOUR ENERGY USAGE BY 1/2

Can a net zero energy buildingbe built?

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FIGURE 2 | National Renewable Energy Laboratory Study

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A study done by the National Renewable Energy Laboratory resulted in a document that estimates the percentage of building floor area that can reach net zero energy (Figure 2).

Notice that the least complex building types like warehouses, education, and service have a better chance to get to net zero energy than the more complicated buildings such as hospitals and laboratories. However, that does not mean energy reduction in those types of building is not possible.

Since they use more energy, small percentages in reduction can equate to large dollar savings. The good news is that 47% of all new floor area has the potential to get to net zero energy. What percentage can get to 50% of the traditional energy used?

REDUCE YOUR ENERGY USAGE BY 1/2

Why go to the extreme ofnet zero energy now?

The answer is - you don’t have to go all the way, just go some of the way. The process which is used to get to net zero energy can be used very effectively to reduce the amount of energy the building will use. The amount of energy the building will use can be engineered to a certain level that is acceptable to the owner. The biggest return on investment comes in the first half of the process.

Diminishing returns are realized as the engineering process gets closer to net zero energy. So, knowing how to get to zero gives us a path to get to a more cost effective reduction, say 50%.

This may sound too easy, but the overall process is simple. There are only two parts.

» Design the building to use as little energy as practical » Add renewable energy to supply the remainder of the energy

The less energy that needs to be produced by renewable sources the easier it is to get to net zero energy. After all there is just so much roof for photovoltaic panels and only so much wind that can be practically harnessed. So if we do the first part of the process well, then we will get a building that operates very efficiently. Looking for beneficial trade-offs will keep the building’s cost in check.

What is the process to get tonet zero energy?

REDUCE YOUR ENERGY USAGE BY 1/2

Modeling software is the designer’s greatest assetin achieving reduced energy use

The answer can be summed up in three words; energy modeling software. Energy modeling software has been rapidly developing over the past 10 years. The software has become very sophisticated and proven accurate for comparative analysis. Once the building characteristics are known the information is entered into the software. The software will analyze each hour of the year based upon cataloged weather data from the locality and calculate the energy used to heat and cool the building as well as the plug loads, lights and any other energy use.

That’s the hard part. The fun begins when the engineer changes a variable, like how the building is oriented on the site. In just a few minutes the software gives a different energy use value that can be compared to the base case value.

Using this method, the most efficient orientation of the building can be determined. Remember the beneficial trade-offs? We have traded building orientation for a decrease in mechanical and electrical system cost by re-orienting the building. In this example, we saved first costs and we also saved operating costs.

Repeating this exercise for many other building variables, we chip away at the energy usage.

How do you design the building touse less energy?

REDUCE YOUR ENERGY USAGE BY 1/2

Adjusting the building criteria one item at a time like lighting intensity, air conditioning system type, roof and wall insulation thickness, occupancy sensor lighting controls, etc., the energy use (and cost) systematically decreases. The result can be significant as shown in Figure 3.

What might the result be when the analysis is complete?

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FIGURE 3 | Yearly BTU Consumption

REDUCE YOUR ENERGY USAGE BY 1/2

We are back to trade-offs again. It is recommended that a cost estimator be teamed with the engineer to estimate the cost differences when each criteria is changed. For example, if 2 inches of roof insulation is added it costs more to build the roof. However, the better performing roof will allow the mechanical and electrical system size to be reduced lowering the cost. The difference in cost can then be calculated.

The energy modeling software will also give an energy cost value that can be compared to the base value. A payback can then be determined. The payback can be considered on a item-by-item basis or items can be grouped together for a combined result. Either way there is adequate information to make an informed decision.

How much will you actually save and how much will this cost?

Will your new energy efficient buildingbe comfortable?

The short answer is yes. In many ways the building will be more comfortable than the traditional building. Codes and standards govern ventilation and comfort criteria requirements and the engineer should always design to these values as a minimum. This will insure a comfortable and healthy environment. However, when designing a high performance building special consideration is given to placement of lighting, air vents, building tightness and solar loading resulting in improved human comfort.

Now you have it, a building that is more comfortable than the traditional building, uses less energy than the traditional building and in some cases cost the same as a traditional building.

Running half the marathon is easy when you know you can run the whole marathon.

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